1 files changed, 111 insertions, 0 deletions
diff --git a/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp b/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp
new file mode 100644
index 000000000..e5e9ca3bb
--- /dev/null
+++ b/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp
@@ -0,0 +1,111 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+#include "qffmpegresampler_p.h"
+#include "playbackengine/qffmpegcodec_p.h"
+#include "qffmpegmediaformatinfo_p.h"
+#include <qloggingcategory.h>
+
+static Q_LOGGING_CATEGORY(qLcResampler, "qt.multimedia.ffmpeg.resampler")
+
+QT_BEGIN_NAMESPACE
+
+using namespace QFFmpeg;
+
+QFFmpegResampler::QFFmpegResampler(const QAudioFormat &inputFormat, const QAudioFormat &outputFormat) :
+    m_inputFormat(inputFormat), m_outputFormat(outputFormat)
+{
+    Q_ASSERT(inputFormat.isValid());
+    Q_ASSERT(outputFormat.isValid());
+
+    m_resampler =
+            createResampleContext(AVAudioFormat(m_inputFormat), AVAudioFormat(m_outputFormat));
+}
+
+QFFmpegResampler::QFFmpegResampler(const Codec* codec, const QAudioFormat &outputFormat)
+    : m_outputFormat(outputFormat)
+{
+    Q_ASSERT(codec);
+
+    qCDebug(qLcResampler) << "createResampler";
+    const AVStream *audioStream = codec->stream();
+
+    if (!m_outputFormat.isValid())
+        // want the native format
+        m_outputFormat = QFFmpegMediaFormatInfo::audioFormatFromCodecParameters(audioStream->codecpar);
+
+    m_resampler = createResampleContext(AVAudioFormat(audioStream->codecpar),
+                                        AVAudioFormat(m_outputFormat));
+}
+
+QFFmpegResampler::~QFFmpegResampler() = default;
+
+QAudioBuffer QFFmpegResampler::resample(const char* data, size_t size)
+{
+    if (!m_inputFormat.isValid())
+        return {};
+
+    return resample(reinterpret_cast<const uint8_t **>(&data),
+                    m_inputFormat.framesForBytes(static_cast<qint32>(size)));
+}
+
+QAudioBuffer QFFmpegResampler::resample(const AVFrame *frame)
+{
+    return resample(const_cast<const uint8_t **>(frame->extended_data), frame->nb_samples);
+}
+
+QAudioBuffer QFFmpegResampler::resample(const uint8_t **inputData, int inputSamplesCount)
+{
+    const int maxOutSamples = adjustMaxOutSamples(inputSamplesCount);
+
+    QByteArray samples(m_outputFormat.bytesForFrames(maxOutSamples), Qt::Uninitialized);
+    auto *out = reinterpret_cast<uint8_t *>(samples.data());
+    const int outSamples =
+            swr_convert(m_resampler.get(), &out, maxOutSamples, inputData, inputSamplesCount);
+
+    samples.resize(m_outputFormat.bytesForFrames(outSamples));
+
+    qint64 startTime = m_outputFormat.durationForFrames(m_samplesProcessed);
+    m_samplesProcessed += outSamples;
+
+    qCDebug(qLcResampler) << "    new frame" << startTime << "in_samples" << inputSamplesCount
+                          << outSamples << maxOutSamples;
+    return QAudioBuffer(samples, m_outputFormat, startTime);
+}
+
+int QFFmpegResampler::adjustMaxOutSamples(int inputSamplesCount)
+{
+    int maxOutSamples = swr_get_out_samples(m_resampler.get(), inputSamplesCount);
+
+    const auto remainingCompensationDistance = m_endCompensationSample - m_samplesProcessed;
+
+    if (remainingCompensationDistance > 0 && maxOutSamples > remainingCompensationDistance) {
+        // If the remaining compensation distance less than output frame,
+        // the ffmpeg resampler bufferises the rest of frames that makes
+        // unexpected delays on large frames.
+        // The hack might cause some compensation bias on large frames,
+        // however it's not significant for our logic, in fact.
+        // TODO: probably, it will need some improvements
+        setSampleCompensation(0, 0);
+        maxOutSamples = swr_get_out_samples(m_resampler.get(), inputSamplesCount);
+    }
+
+    return maxOutSamples;
+}
+
+void QFFmpegResampler::setSampleCompensation(qint32 delta, quint32 distance)
+{
+    const int res = swr_set_compensation(m_resampler.get(), delta, static_cast<int>(distance));
+    if (res < 0)
+        qCWarning(qLcResampler) << "swr_set_compensation fail:" << res;
+    else {
+        m_sampleCompensationDelta = delta;
+        m_endCompensationSample = m_samplesProcessed + distance;
+    }
+}
+
+qint32 QFFmpegResampler::activeSampleCompensationDelta() const
+{
+    return m_samplesProcessed < m_endCompensationSample ? m_sampleCompensationDelta : 0;
+}
+
+QT_END_NAMESPACE